The general objective is to use Paramecium to advance knowledge of cellular and clonal development, genetics, and evolution. About 100 mutant genes are being tested for allelism and linkage. These and multiple marker stocks will be used for chromosome mapping. Studies of cytotaxis center around (1) the role of the orientation of the cell cortex on the direction of movement of food vacuoles, (2) the movement, localization and orientation of trichocysts, and (3) a mutational analysis of oral primordium determination, inheritance and development. Studies will be made on nuclear differentiation for trichocyst discharge initiated by plasmamembrane interaction between cells. Standard cultural, genetic, cytological and molecular methods will be used, including transmission electron microscopy of thin sections, and of freeze-fracture preparations of membranes, and possibly high voltage EM of thicker sections.